Messier 50 or M 50, also known as NGC 2323 or the Heart-shaped Cluster, is an open cluster of stars in the constellation Monoceros.

It was recorded by G. D. Cassini before 1711 and independently discovered by Charles Messier in 1772[b] while observing Biela's Comet.

[3] M50 is about 2,900 light-years away from Earth[2] and is near to but narrowly not estimated to be gravitationally tied to the Canis Major (CMa) OB1 association.

[4] The cluster has 508 confirmed and 109 probable members – their combined mass is more than 285 M☉, the mean stellar density would thus be 1.3 stars per cubic parsec.

[4] It is around 140 million years old,[1] with two high-mass white dwarfs[7] and two chemically peculiar stars.